Electrical resistance element.



UNITED STATES PATENT oruucn ALBERT I. MARSH, OF DETROIT, MICHIGAN, ASSIGNOB T0 HOSKINS murncrmmio COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

mc'rmcn. imsrsnucl murmur.

1,057,756. 80 Drawing.

Be it known that I, ALBERT L. 'MAnsH, a citizen of the United States, residing at Detroit,-in the county of Wayne and State of Michigan, have invented a. new and useful Improvement in Electrical Resistance Ele-- ments, of which the following is a specij'i cation.

My invention consists in a novel resistance element adapted for general use for which articles of the class are intended,"

more especially, suited for use in heating apalliances. For this purpose, it is well unerstood that the principal requirement is durshility, end this durability depends upon '50 many varying conditions that it can only he determined by sctual tests under epproximatel'y the conditions of use.

in my Patent No. 811,859, wherein is de scribed e resistsnce element of nickel andchromium in which the desirable percentages-mentioned ere chromiumld and 15%, it is also stated that iron-chromium alloys are not sstisfsctoryJ in my applicetion, filed on even date herewith end allotted Serial Number 723394;, I have pointed out that I have since discovered that in certain "dlfi'erent proportions than said application mentioned, iron end. chromium form fairly durable alloys,v

I heye further discovered that if iron chromium alloys with the chromium of even smaller eroentages than those mentioned in the app icetion referred to have added to them small percents es of either silicon or aluminum, both .the ife and the resistivity of the elements are greatly augmented. in 'the present state of my knowledge on the subject, I prefer to add about 5% of either aluminum or silicon to the iron-chromium alloy. Preferably, the iron-chromium base will be made in the percentages set forth as preferable in the application'referred to,

' which is an iron-chromium alloy inherently ofat durability, that is, the chromium wilflde 25% and the iron 75% of the total of those constituents. When 5% of silicon is added to such an alloy, a specific resistance of 112 microhms per centimeter cube is obtained, and when the added element is aluminum of equal quantity, the resistivity is 121 microhms r centimeter cube, and in both cases the e ement is made-extraordiments in common with. verv lame number Specification 0! Letters Patent.

Application filed September'SO, 1912, Sci-15110. 723,186.

- Patented Apr. 1, 1913.

of elements of other types and have obtained at 1000' C. the greatest life within my knowl'ed e from the resistance element herein speci ed. It is to beunderstood, however, that while I prefer to use as the base" the iron-chromium alloy of'my application aforesaid, the aluminum and silicon have such an extraordinary efiect in prolonging the life of the iron-chromium element atv high temperatures that it is not necessary to use the iron-chromiurn in the percentages within that application, but the i I chromium maybe used with the iron in. such percentages as would render the resistance element, with the aluminum or silicon omitted, quite uselessfor pract cal purposes.

I am aware that'silicon and aluminum do not fall into any common chemical-cute gory, but I find that for the particular purpose. herein mentioned they are equivalents and, therefore, in the claims I shall speak of materials having the roperties herein described of eluininum and of any better way of expressin' the com-- mon properties. The exact quality of these metals which for this purpose renders them equivalent, l are uneiile definitely to'stste.

A large factor, however, in the durability of eny resistance elements at lu h temperstures IS the character of its 02rd coating or silicon for want scale, and though there are many nletsls'oil I rous scale, and alone is useless as e resist- 1 once element. Chromium has ulrnost no scale at all, fromwhich it muy be presumed that such as does exist is tough and udherent, ulthough the scale is of heeutifiilly' soft-appearing texture. The scales of silicon and aluminum, on the other hend, are of well known chemical character, sand quite tough and impermeable. Now, by actual experience, I have learned that forthe purpose of increasing the life of an iron chromium alloy silicon and aluminum are equivalents, as. already stated, and this is the fact that the scale of the iron-chromium alloy to jwhich either silicon or aluminum has-been added is much more touch and inl- ;-probably, although, not certainly,- because of 'penetrahle than when these omitted. 1 e

What -I claimas' new and desire to secure by Letters Petent is.- I 1. A resistance element com osed of an iron-chromium alloy to whic has "been added a relatively-smell quantity of a, metal having the properties hereinabove described of aluminum and silicon.

.2. An electrical resistance element formed of an iron-chromium alloy, 'With the chromium in the roportion of approximately one third of t e 1mm, and an added material having the hereinabove described properties of aluminum and silicon added 111 metals are memes my hand and aflixed my seal this-18th day of September, A. D. 1912.

" ALBERT L'MARSHL [in 5.]

proportion of about 5%. of the totel of the Q In testimony whereof I have hereunto set I In the presence of two "subscribing-wit nesses:

J. G. Anon, J. LANDESMAN. 

